Reed switch with improved contact and end cap structure

ABSTRACT

A sealed contact reed switch is disclosed in which the contact springs include two sets of overlapping contacts, the ends of the encapsulating vessel are sealed with dimpled end caps and the contact springs and external leads have portions positioned in pockets formed by the dimples in the end caps.

United States Patent Inventor Edward George Walsh Galena, Ohio June 8, 1970 Jan. 4, 1972 Bell Telephone Laboratories, Incorporated Murray Hill, NJ.

Appl. No. Filed Patented Assignee REED SWITCH WITH IMPROVED CONTACT AND END CAP STRUCTURE 12 Claims, 6 Drnwlng Figs.

[1.8. CI 335/151 Int. Cl 1101b 1/66 Field of Search 335/154,

References Cited UNITED STATES PATENTS 3,345,593 10/1967 Grengg Primary Examiner-Bemard A. Gilheany Assistant Examiner-R. N. Envall, Jr. Attorneys-R. J. Guenther and Edwin B. Cave ABSTRACT: A sealed contact reed switch is disclosed in which the contact springs include two sets of overlapping contacts, the ends of the encapsulating vessel are sealed with dimpled end caps and the contact springs and external leads have portions positioned in pockets formed by the dimples in thc end caps.

tion between the contact spring,

I REED SWITCH wIT IIMpRovEn CONTACT AND END CAP STRUCTURE BACKGROUND OF THE INVENTION 1 F ield of the Invention This invention pertainsto" miniature switching devices and relates in particular toth'ose inwhich contact springs are sealed in a hollow vessel.

- the two overlapping contact springs are separated by an airgap and switching actions; i.e., engagement and disengagement of the contacting portion, occurs in response to appropriate magnetic stimulation of the two contact springs.

While reed switches have gained wide acceptance, complete reliability has never been achieved. For example, the seals which join the hollow vessel and the contact springs are especially delicate. Consequently, if particular care is not exercised during handling'and installation, the seals are easily damaged. Seal damage is not readily apparent, so defective reed switches are often installed without detection. Where large numbers of reed switches are involved, the cost of locating and replacing defective reed switches can easily assume substantial proportions.

Accordingly, one object of this invention is to improve the union between components in a sealed contact reed switch, thereby achieving greater reliability and attendant cost reductions.

Efficiency is as important as reliability, especially in miniaturized versions of scaled contact reed switches. Because of their small size, however, it has been difficult to minimize power requirements without reducing the contact force. For example, as contact spring length decreases, retractile force increases which reduces the contact force for the same power. Where the magnitude of the retractile force increases beyond the designed minimum, power is wasted when closing the contacts. Consequently, unnecessary costs are incurred.

Accordingly, another object of this invention is to decrease the size of a sealed contact reed switch without proportionately increasing retractile forces in the contact springs or decreasing the contact force.

Power efficiency is also affected by the way in which the contact springs interact." For example, if the contacting surfaces are not parallel, a forceg'reater than the design minimum is required to completely close the contact springs and keep them closed. Consequently, nonaligned contacting surfaces waste power and cause-unnecessary expense.

Accordingly, another object of the invention is to improve the alignment between interacting contact switches in order to minimize power consumption and thus reduce cost.

SUMMARY OF THE INVENTION According to a preferred embodiment of this invention, the power necessary to operate a miniaturized sealed contact reed switch is reduced and' reliability folded contactspring, an external contact lead, the end of a hollow vessel and a separate end cap having a contact support extending into the hollow vessel to form internal and external pockets.

In accordance with one feature of this invention, the juncthe external contact lead, the hollow vessel and the end cap is improved by forming the end cap and contact support from a metallic material, separately attaching the end cap to the hollow vessel and attaching the external lead and the contact springto the contact support with the external contact lead located inside the external I pocket. The metal-to-metal union between the contact support and the external lead increases seal strength; locating the union inside the external pocket guards the seal between the is improved by combining a 2 external lead and the contact support from externaldamage, and separately joining the end capand the hollow vessel reduces the likelihood that stresses arising from forces induced in the contact support willreach the seal which joins the end cap and the hollow vessel. I

According to another feature of this invention, operating power requirements are reduced by reducing the amount of retractile force available at the contacting surfaces; More particularly, a contact spring having a contact atone end' is attached to the contact support with a'portion of the "contact spring located between the contact support and the contact folded backward into the internal pocket. By folding the contact spring backward into the internal pocket, effective overall length is increased between the contact supportand the contact. As a result, the effective length of the contact spring is increased thereby reducing the magnitude of retractile force available at the contact.

According to another feature of this invention, operating power requirements are reduced by attaching the middle section of a U-shaped contact spring having a contact at each end to the contact support with portions of the contact spring lying between the contact support and each of the two contacts .folded backward into the internal pocket. Locating folded portions on opposite legs of the contact spring in the internal pocket increases the effective length of both'legs. As a result, the amount of retractile force available at the two contacts is reduced.

According to another feature of this invention, operating power requirements are reduced by improving the alignment between cooperating contacts. More specifically, at least one contact is ofiset from the contact spring; at least one aligning tab having a bearing surface disposed'in parallel with both the offset contact and the inner wall of the hollow vessel is located on the contact spring, and at least one notch is cut in the edge of the contact spring adjacent to thealigning tab. The offset permits the contact to readily cooperate with a counterpart contact positioned by reference to the inner wall of the hollow vessel; the bearing surface on the'aligning tab'helps to align the offset contact in parallel with other contacts locatedby reference to the inner wallof the hollow vessel, and the notch locally increases the flexibility of the contact spring thereby improving parallelism between the aligning tab and the inner vessel wall and the offset contact spring and counterpart contacts as they engage.

A better understanding of these and other features of the invention will be assisted by the following description of the drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view taken in section showing a sealed contact reed switch constructed in accordance with this invention;

FIG. 2 is a perspective view of part of a contact spring;

FIG. 3 is a perspective view of an end cap and contact support;

FIG. 4 is an end elevation view taken in section along the line 44 in FIG. 1 illustrating the details of the interacting contact springs at one end of the sealed contact reed switch shown in FIG. 1;

FIG. 5 is an end elevation view taken in section along the line 5-5 in FIG. 1 illustrating the details of the interacting contact springs at the other end of the sealed contact reed switch shown in FIG. 1; and

FIG. 6 is a partial end elevation view of the sealed contact reed switch shown in FIG. 1 illustrating an alternative form' of end cap.

DETAILED DESCRIPTION Referring to FIG. 1, a sealed contact reed switch 10 isdisclosed which comprises a vessel l l, two contact sprin'gs l2, two end caps 13 and two external contact leads 14. All of the foregoing components are rigidly joined together to form a hermetically sealed switching'device in which electrical current can be made to pass from one external contact lead to the other in response to the application of a magnetic field.

The vessel 11 is hollow and is sealed at both ends by the two end caps 13. Advantageously, the vessel 11 is made of an impervious material, such as glass. Coming 7052 has proved to be a particularly suitable glass.

Each end cap 13 is made of a metal which is both electrically conducting and compatible with the material from which the vessel 11 is made. Where the vessel 1 l is made of Coming 7052 glass, for example, Kovar can be advantageously used to fabricate the end caps 13. Both end caps 13 are identical, so a description of one will suffice for the other.

As best seen in FIGS. 1 and 3, each end cap 13 is cylindrical in form. The center, however, includes a contact support 15. As best seen in FIG. 3, the contact support 15 is a dimple or raised portion having the shape of a truncated cone which rises internally within the end cap 13 to fonn an internal pocket 16 and an external pocket 17. As illustrated in FIG. 1, the end cap 13 has an outside diameter equal to the inside diameter of the vessel 11. As a consequence, it readily slips into the end of the vessel 11 where it is fused in place. That is, when the end cap 13 is inserted, the vessel 11 is heated until the wall material melts and combines with the end cap material to form a rigid bond. When both ends of the vessel 11 are closed by the end caps 13, a hermetically sealed space is formed within the vessel 11 which is suitable for accommodating the contact springs 12.

Two contact springs 12 appear in the embodiment disclosed in FIG. 1. The two act in concert and together establish parallel electrical paths through the vessel 1 1. Both are identical, so a description of one will suffice for the other.

As best seen in FIG. 1, each contact spring 12 is roughly W- shaped and is attached at its closed end to a contact support 15. Each is made of a flexible, magnetic, and electrically conducting metal such as Wilbur B. Driver No. 52 alloy or alloy or Remendur, and is rigidly sealed to the contact support 15. For strength, the seal is advantageously a weld. A welded seal is particularly strong and will be unlikely to fail except under the most extreme stresses.

The two legs formed by the W shape of the contact spring 12 are of unequal length, but each contains a contact 18 at its free end. Moreover, as best seen in FIGS. 1 and 2, each leg contains a primary fold 22 and a secondary fold 23. Both folds are located between the contact 18 and'the closed center portion of the contact spring which attaches to the contact support 15. The primary fold 22, moreover, is located in the internal pocket 16.

The primary and secondary folds cooperate to increase the overall effective length of each contact spring leg. Specifically, the secondary fold 23 turns the contact spring 12 away from the interior portion of the vessel 11, while the primary fold 22 turns the contact spring 12 back toward the interior of the vessel 11. As a consequence, the effective length of the contact spring 12, as measured from its point of attachment on the contact support 15 to the contact 18, is substantially increased. With the increase in effective length, the retractile forces available at the contacts 18 are reduced.

The contacts 18 in both contact springs 12 are arranged in complementary pairs and the contacts in each pair are separated by an airgap. As can be seen from FIG. 1, a contact 18 on the short leg of one contact spring 12 is paired in overlapping relationship with a contact 18 on the long leg of the other contact spring 12. Thus electrical current can flow from one external lead 14 to the other even if one contact pair fails to operate.

In addition to its length, the short leg of each contact spring 12 differs from the long leg in three other respects: first, the contact 18 is bent to form an offset contact surface 24; second, two aligning tabs 25 are located between the contact 18 and the primary fold 22; and, finally, two sets of notches 26 are located on either side of the contact spring 12 adjacent to the aligning tabs 25. It will be understood, however, that either one or bothnotch sets can be eliminated if desired.

The aligning tabs 25 reference the contact surface 24 to the inner wall of the vessel 11, while the notches 26 help improve the interaction between l the contact surface 24, and an associated contact 18 and (2) the inner wall and the aligning tabs 25. As best seen in FIG. 2, each aligning tab 25 has two bearing edges 27. The contact surface 24, the aligning tabs 25 and the bearing edges 27 are arranged so that the bearing edges 27 lie in a plane disposed I parallel to a plane containing the contact surface 24 and 2) spaced therefrom a predetermined distance.

As shown in FIGS. 1, 4 and 5, both the bearing surfaces 27 and the contact 18 associated with the contact surface 24 engage portions of the inner wall of the vessel 11. By using the wall as a common reference point and spacing the contact surface 24 on one contact spring 12 a predetermined distance from the bearings edges 27, the spacing between the contact surface 24 and the associated contact 18 on the other contact spring 12 is readily and precisely established.

The notches 25 located farthest from the contact surface 24 decrease the cross-sectional area of one contact spring 12. Consequently, the contact spring 12 can readily deflect along its long axis, thereby helping the bearing edges 27 to lie flat on the inner wall of the vessel 1 1.

In the operation, a magnetic flux (from a source not shown) is passed longitudinally through the sealed contact reed switch 10 via the contact springs 12. As the flux passes through the contact springs 12, a magnetic force of attraction is established between adjacent ends. When the force level reaches a sufficient magnitude, each contact 18 swings into engagement with its associated contact surface 24 and closes an electrical circuit linking the two external leads 14.

As the contact springs 12 engage each other, the notches 26 in the set nearest to the contact surface 24 help compensate for misalignment between each contact surface 24 and its mating contact 18. Specifically, torsional stiffness of the contact spring 12 is reduced because of the narrower width of the contact spring 12 at the notch location. Consequently, the offset contact 18 is readily able to rotate and thus adjust misalignment between the contact surface 24 and its mating contact 18.

In the embodiment disclosed, the contact springs 12 are connected to external circuitry through the external contact leads 14. AS illustrated in FIG. 1, each external contact lead 14 is attached to the contact support 15 in an external pocket 17. The union between the contact lead 14 and the contact support 15 is rigid, as, for example, by a weld. Consequently, the seal joining the two components is extremely strong. Moreover, the location of the seal in the external pocket 17 protects the seal from external hazards. Finally, since the contact lead 14 need not be compatible to one vessel material, it can be made of a ductile material which will easily plastically deform and thereby limit stresses that can be applied to one seal at the vessel 1 1.

An alternative form of the sealed contact reed switch 10 is illustrated in FIG. 6 in which external contact leads are not required. Instead, the end caps 15 have an inside diameter equal to the outside diameter of the vessel 11. In that arrangement, each end cap 15 is fitted over one end of the vessel 11 and sealed in place by heating the material of the vessel 11 until fusion occurs. With the type of construction illustrated in FIG. 6, the sealed contact reed switch 10 is especially adapted for installation in a fuse-type holder (not shown).

Finally, the contact spring 12 need not be a single unitary component. Instead, each leg can be a separate entity. In the embodiment illustrated in FIG. 6, for example, the two legs 12a and 12b are separate from each other and are independently attached to the contact support 15.

In summary, a new switch design has been disclosed in which specific components cooperate to form a simple, more reliable sealed contact reed switch. While the embodiments disclosed are principal ones, it is expected that others will occur to those skilled in the art which fall within the scope of the invention.

1 claim:

1. Switching apparatus comprising a hollow vessel, a contact lead located externally to said vessel, a separate end cap closing one end of said vessel, a magnetically responsive contact spring located within said vessel, a contact located on one end of the contact spring, and a contact support joining the end cap, the contact lead and the contact spring in a unitary assembly, characterized in that said contact support cooperates with the wall of said vessel to form an internal pocket and said contact spring includes a folded portion located in said internal pocket, whereby the overall effective length of said contact spring is increased without increasing the length of said vessel.

2. Switching apparatus in accordance with claim 1 wherein said contact support is an integral part of said end cap, extends into said vessel a finite distance and is separated from the inner wall of said vessel, whereby said internal pocket is formed between said contact support and the inner wall of said vessel.

3. Switching apparatus in accordance with claim 1 wherein said contact spring includes two primary folds separated by two secondary folds and each primary fold is located in said internal pocket, whereby the overall effective length of said contact spring is further increased without increasing the length of said vessel.

4. Switching apparatus in accordance with claim 3 wherein the point of attachment between said contact support and said contact spring is located between said two secondary folds.

5. Switching apparatus in accordance with claim 1 wherein said contact support is a dimple pressed into the surface of said end cap to form an external pocket within the body of said vessel and said contact lead is attached to said contact support within the confines of said external pocket.

6. Switching apparatus in accordance with claim 5 wherein said dimple takes the form of a cone and said contact lead is attached to one side of the peak of said cone and said contact spring is attached to the other side.

7. Switching apparatus in accordance with claim 1 wherein said contact is bent into an approximate Z-shape to form an offset contact surface.

8. Switching apparatus in accordance with claim 7 wherein the free end of said contact spring includes a pair of aligning tabs, each having bearing edges disposed in parallel with said offset contact surface and in contact with the inner wall of said vessel, whereby the location of said offset contact surface is referenced to said inner wall.

9. Switching apparatus in accordance with claim 8 wherein the edge of said contact spring has at least one notch cut therein adjacent to an aligning tab whereby flexiblity of said contact spring is locally increased, thereby improving the ability of parts of said contact spring to achieve flush engagement with appropriate mating parts.

10. Switching apparatus in accordance with claim 8 wherein said aligning tabs are bent upwardly from the surface of said contact spring to form a pair of adjacent notches, whereby the aligning tabs can be formed and torsional flexibility of said contact spring increased in a single operation.

1 1. Switching apparatus in accordance with claim 7 wherein said free end of said contact spring further includes at least one aligning tab having a bearing surface disposed in parallel with said offset contact surface and in contact with the inner wall of said vessel.

12. Switching apparatus in accordance with claim 11 wherein each aligning tab is bent upwardly from the surface of said contact spring to form a notch, whereby torsional flexibility of said contact spring can be increased and formation of the aligning tab can be achieved in a single operation. 

1. Switching apparatus comprising a hollow vessel, a contact lead located externally to said vessel, a separate end cap closing one end of said vessel, a magnetically responsive contact spring located within said vessel, a contact located on one end of the contact spring, and a contact support joining the end cap, the contact lead and the contact spring in a unitary assembly, characterized in that said contact support cooperates with the wall of said vessel to form an internal pocket and said contact spring includes a folded portion located in said internal pocket, whereby the overall effective length of said contact spring is increased without increasing the length of said vessel.
 2. Switching apparatus in accordance with claim 1 wherein said contact support is an integral part of said end cap, extends into said vessel a finite distance and is separated from the inner wall of said vessel, whereby said internal pocket is formed between said contact support and the inner wall of said vessel.
 3. Switching apparatus in accordance with claim 1 wherein said contact spring includes two primary folds separated by two secondary folds and each primary fold is located in said internal pocket, whereby the overall effective length of said contact spring is further increased without increasing the length of said vessel.
 4. Switching apparatus in accordance with claim 3 wherein the point of attachment between said contact support and said contact spring is located between said two secondary folds.
 5. SWitching apparatus in accordance with claim 1 wherein said contact support is a dimple pressed into the surface of said end cap to form an external pocket within the body of said vessel and said contact lead is attached to said contact support within the confines of said external pocket.
 6. Switching apparatus in accordance with claim 5 wherein said dimple takes the form of a cone and said contact lead is attached to one side of the peak of said cone and said contact spring is attached to the other side.
 7. Switching apparatus in accordance with claim 1 wherein said contact is bent into an approximate Z-shape to form an offset contact surface.
 8. Switching apparatus in accordance with claim 7 wherein the free end of said contact spring includes a pair of aligning tabs, each having bearing edges disposed in parallel with said offset contact surface and in contact with the inner wall of said vessel, whereby the location of said offset contact surface is referenced to said inner wall.
 9. Switching apparatus in accordance with claim 8 wherein the edge of said contact spring has at least one notch cut therein adjacent to an aligning tab whereby flexiblity of said contact spring is locally increased, thereby improving the ability of parts of said contact spring to achieve fluSh engagement with appropriate mating parts.
 10. Switching apparatus in accordance with claim 8 wherein said aligning tabs are bent upwardly from the surface of said contact spring to form a pair of adjacent notches, whereby the aligning tabs can be formed and torsional flexibility of said contact spring increased in a single operation.
 11. Switching apparatus in accordance with claim 7 wherein said free end of said contact spring further includes at least one aligning tab having a bearing surface disposed in parallel with said offset contact surface and in contact with the inner wall of said vessel.
 12. Switching apparatus in accordance with claim 11 wherein each aligning tab is bent upwardly from the surface of said contact spring to form a notch, whereby torsional flexibility of said contact spring can be increased and formation of the aligning tab can be achieved in a single operation. 